Method and system for hydrolytic saccharification of a cellulosic biomass

ABSTRACT

A method and system for hydrolyzing cellulose and/or hemicellulose contained in a biomass into monosaccharides and oligosaccharides by using high-temperature and high-pressure water in a subcritical condition is provided. In hydrolyzing cellulose or hemicellulose into saccharides by using high-temperature and high-pressure water in a subcritical condition, a large amount of slurry is cooled into a condition below the subcritical condition by subjecting the slurry contained in a pressure vessel under a high-temperature and high-pressure condition to flash evaporation in a pressure vessel charged with a slurry of a cellulosic biomass and heated halfway. It is possible to prevent saccharides from degrading into organic acids and to save energy by recovery of thermal energy. The cellulosic biomass is charged into a water-permeable vessel and then the water-permeable vessel is encapsulated into the pressure vessel together with water.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydrolyzing method and system forefficiently producing saccharides from biomasses, particularlycellulosic biomasses, used as raw materials.

2. Description of the Related Art

As part of biomass energy utilization, attempts have been made to obtainethanol (bioethanol) by hydrolyzing cellulose or hemicellulose, whichare major constituents of plants. Ethanol thus obtained is planned to beutilized as a fuel to be mixed into an automotive fuel or as analternative fuel for gasoline.

Major constituents of plants include cellulose (a polymer of glucose,which is a C6 saccharide comprising six carbon atoms), hemicellulose (apolymer of a C5 saccharide comprising five carbon atoms and a C6saccharide), lignin, starch, and the like. Ethanol is produced fromsaccharides, such as a C5 saccharide, C6 saccharide, and oligosaccharidewhich is a complex of these saccharides, used as raw materials, by thefermentation action of yeast fungi or the like.

Three methods of hydrolyzing a cellulosic biomass comprising cellulose,hemicellulose or the like into saccharides are about to be utilizedindustrially, which include: 1) a method of hydrolyzing such a biomassby the oxidative power of a strong acid, such as sulfuric acid; 2) amethod of hydrolyzing such a biomass by yeast; and 3) a method utilizingthe oxidative power of supercritical water, subcritical water or thelike. However, the hydrolytic method 1) using the acid indispensablyrequires a treatment for neutralizing the added acid after hydrolysis ofcellulose or hemicellulose into saccharides and before fermentation ofthe saccharides into ethanol because the added acid acts as an inhibitoragainst the fermentation by yeast or the like. The cost of such atreatment makes it difficult to put this method into practice in view ofthe economical aspect.

The outlook for industrial-scale realization of the hydrolyzing method2) using yeast is still vague in view of the cost efficiency because aneffective yeast for the method 2) has not been found yet and, if found,such a yeast is expected to incur a high production cost thereof, thoughthe method 2) can be realized by a normal-temperature andnormal-pressure process.

As the method 3) of hydrolyzing cellulose or the like into saccharidesby using supercritical or subcritical water, patent document 1 hasdisclosed a method of producing water-insoluble polysaccharides, whichis characterized by hydrolysis of cellulosic powder by bringing thepowder into contact with pressurized hot water at 240 to 340° C. Patentdocument 2 has disclosed a method including: hydrolyzing biomass chipswith hot water pressurized to a saturated vapor pressure or more at 140to 230° C. for a predetermined time period to extract hemicellulose; andthen conducting hydrolysis using pressurized hot water heated to atemperature not less than the cellulose hydrolyzing temperature toextract cellulose. Patent document 3 has disclosed a method of producingglucose and/or water-soluble cello-oligosaccharide, which ischaracterized in that cellulose having a mean polymerization degree ofnot less than 100 is hydrolyzed by the steps of: bringing the celluloseinto contact with supercritical or subcritical water at a temperature ofnot lower than 250° C. and not higher than 450° C. and a pressure of notless than 15 Mpa and not more than 450 MPa for a time period of not lessthan 0.01 seconds and not more than 5 seconds; cooling the cellulose;and then bringing the cellulose into contact with subcritical water at atemperature of not lower than 250° C. and not higher than 350° C. and apressure of not less than 15 Mpa and not more than 450 MPa for a timeperiod of not less than 1 seconds and not more than 10 minutes.

On the other hand, patent document 4 has disclosed a method of treatinga biomass-type waste, which includes: placing a subject for treatmentcontaining a solvent comprising low-molecular-weight alcohol as a majorcomponent and the biomass-type waste into a closed vessel; and treatingthe subject by pressurizing and heating the interior of the closedvessel so that the low-molecular-weight alcohol reaches itssupercritical condition. Also, patent document 5 has disclosed a methodof hydrolyzing and liquefying a biomass, which includes treating acellulosic biomass by using a mixed solvent prepared by adding 5-20% byvolume of water to a C1 to C8 aliphatic alcohol under the supercriticalor subcritical condition of the alcohol.

-   Patent document 1: Japanese Patent Provisional Publication No.    2000-186102-   Patent document 2: Japanese Patent Provisional Publication No.    2002-59118-   Patent document 3: Japanese Patent Provisional Publication No.    2003-212888-   Patent document 4: Japanese Patent Provisional Publication No.    2001-170601-   Patent document 5: Japanese Patent Provisional Publication No.    2005-296906

As compared with the hydrolytic method using a strong acid, the methodof hydrolytic saccharification of cellulose and hemicellulose as majorconstituents of a biomass by using high-temperature and high-pressuresupercritical or subcritical water requires a lower processing cost andis a more environment friendly because this method does not require anyacid neutralizing treatment. However, this method has a drawback thatwithout cooling immediately after the completion of hydrolysis,saccharides produced thus far would degrade into organic acids or thelike because the use of supercritical or subcritical water causescellulose and hemicellulose to hydrolyze into saccharides completely inseveral seconds to several minutes by its strong oxidative power.

With a laboratory-scale small system for hydrolysis, it seems that suchdegradation can be prevented by rapidly cooling supercritical orsubcritical water in the heating vessel. With an industrial-scalehydrolysis system, however, it is very difficult to cool a large amountof supercritical or subcritical water in a short time. For this reason,the cellulosic biomass hydrolysing method using high-temperature andhigh-pressure supercritical or subcritical water, when applied to aplant-scale system, will give a low yield of saccharides, which formsone of the factors that prevent this method from being put to practice.

In using a large amount of supercritical or subcritical water, theslurry has to be heated with a large amount of energy, which forms afactor raising the processing cost. The cellulosic biomass hydrolyzingmethod, which subjects a slurry containing alcohol or the like as asolvent to hydrolysis under a supercritical or subcritical condition,requires a very high vapor pressure, hence, requires a larger amount ofenergy and has to use a system having a high pressure resistance.

It is an object of the present invention to provide a method and systemfor hydrolyzing cellulose and/or hemicellulose contained in a biomassinto monosaccharides and oligosaccharides (hereinafter will be referredto as “saccharides”) by using high-temperature and high-pressure waterin a subcritical condition, which method and system is excellent inthermal efficiency and yields of saccharides.

SUMMARY OF THE INVENTION

The inventor of the present invention has found out that in hydrolyzingcellulose or hemicellulose into saccharides by using high-temperatureand high-pressure water in a subcritical condition it is possible tocool a large amount of slurry to a temperature not higher than thecellulose hydrolyzing temperature thereby preventing saccharides fromdegrading into organic acids or the like as well as to save energy byrecovery of thermal energy, by subjecting the slurry contained in apressure vessel under a high-temperature and high-pressure condition toflash evaporation in a pressure vessel that is charged with a slurry ofa cellulosic biomass and heated halfway. Thus, the present invention hasbeen accomplished.

Specifically, the present invention is directed to a method ofhydrolytic saccharification of a cellulosic biomass with use of pluralpressure vessels, the method comprising a charging step, a heating-upstep, a hydrolyzing step, a temperature lowering step, and a dischargingstep, which are performed sequentially by each of the pressure vessels,wherein:

the charging step is a step of charging a slurry prepared by grindingthe cellulosic biomass and then mixing the cellulosic biomass thusground with water (hereinafter will be referred to as “slurry”) intoeach of the pressure vessels;

the heating-up step is a step of hermetically closing the pressurevessel and heating up the slurry;

the hydrolyzing step is a step of hydrolyzing cellulose and/orhemicellulose contained in the cellulosic biomass into saccharides by anoxidative power of high-temperature and high-pressure water;

the temperature lowering step is a step of flash-evaporating thehigh-temperature and high-pressure slurry contained in the pressurevessel to flash evaporation to lower the temperature thereof;

the discharging step is a step of removing the slurry out of thepressure vessel;

while any one of the plural pressure vessels performs the charging step,any one of the other pressure vessels performs the discharging step soas to allow heat exchange to occur between the slurry to be charged intothe pressure vessel performing the charging step and the slurry to bedischarged from the pressure vessel performing the discharging step; and

while any one of the plural pressure vessels performs the heating-upstep, any one of the other pressure vessels performs the temperaturelowering step and allows heat recovery to be made by supplying flashvapor discharged from the pressure vessel performing the temperaturelowering step to the pressure vessel performing the heating-up step(claim 1).

The present invention is also directed to a system for hydrolyticsaccarification of a cellulosic biomass, comprising plural pressurevessels each configured to perform sequential steps including:

a charging step of charging a slurry prepared by grinding the cellulosicbiomass and then mixing the cellulosic biomass thus ground with waterinto the pressure vessel;

a heating-up step of hermetically closing the pressure vessel andheating up the pressure vessel;

a hydrolyzing step of hydrolyzing cellulose and/or hemicellulosecontained in the cellulosic biomass into saccharides by an oxidativepower of high-temperature and high-pressure water;

a temperature lowering step of flash-evaporating the high-temperatureand high-pressure slurry contained in the pressure vessel to lower thetemperature thereof; and

a discharging step of removing the slurry out of the pressure vessel,wherein:

while any one of the plural pressure vessels performs the charging step,any one of the other pressure vessels performs the discharging step soas to allow heat exchange to occur between the slurry to be charged intothe pressure vessel performing the charging step and the slurry to bedischarged from the pressure vessel performing the discharging step; and

while any one of the plural pressure vessels performs the heating-upstep, any one of the other pressure vessels performs the temperaturelowering step and allows heat recovery to be made by supplying flashvapor discharged from the pressure vessel performing the temperaturelowering step to the pressure vessel performing the heating-up step(claim 23).

In the method and system for hydrolytic saccharification of a cellulosicbiomass according to the present invention, five process steps areperformed in each of the plural pressure vessels. By connecting thepressure vessel at the temperature lowering step to another pressurevessel at the heating-up step, the slurry in the pressure vessel at thetemperature lowering step can be rapidly cooled by flash evaporation. Atthe same time, the slurry in the pressure vessel performing theheating-up step can be heated by high-temperature flash vapor, wherebythe energy required to heat the slurry can be saved.

By reducing the internal pressure of the pressure vessel from the gasphase portion, there is no danger that the dissolved components andsolid contents of the slurry move to clog the nozzle and piping forpassage of flash vapor. Further, there is no need to provide a specialtemperature controller or the like. In supplying the preheated side(i.e., the pressure vessel at the heating-up step) with flash vapor, thepreheating of the slurry becomes more effective by supplying flash vaporinto the slurry.

The method and system for hydrolytic saccharification of a cellulosicbiomass according to the present invention allows heat exchange to occurbetween the slurry to be discharged (drained) from the pressure vesselat the discharging step and the slurry to be charged into anotherpressure vessel at the charging step, thereby making it possible tofurther save the energy required to heat the slurry.

The present invention is also directed to a method of hydrolyticsaccharification of a cellulosic biomass with use of plural pressurevessels, the method comprising a charging step, a heating-up step, ahydrolyzing step, a temperature lowering step, and a discharging step,which are performed sequentially by each of the pressure vessels,wherein:

the charging step is a step of charging the cellulosic biomass into awater-permeable vessel and then encapsulating the water-permeable vesseland water into each of the pressure vessels;

the heating-up step is a step of hermetically closing the pressurevessel and heating up the cellulosic biomass and water;

the hydrolyzing step is a step of hydrolyzing cellulose and/orhemicellulose contained in the cellulosic biomass into saccharides by anoxidative power of high-temperature and high-pressure water;

the temperature lowering step is a step of flash-evaporatinghigh-temperature and high-pressure water contained in the pressurevessel to lower the temperature thereof;

the discharging step is a step of removing the water and thewater-permeable vessel out of the pressure vessel;

while any one of the plural pressure vessels performs the charging step,any one of the other pressure vessels performs the discharging step soas to allow heat exchange to occur between water to be charged into thepressure vessel performing the charging step and high-temperature waterto be discharged from the pressure vessel performing the dischargingstep; and

while any one of the plural pressure vessels performs the heating-upstep, any one of the other pressure vessels performs the temperaturelowering step and allows heat recovery to be made by supplying flashvapor discharged from the pressure vessel performing the temperaturelowering step to the pressure vessel performing the heating-up step(claim 2).

The present invention is also directed to a system for hydrolyticsaccarification of a cellulosic biomass, comprising plural pressurevessels each configured to perform sequential steps including:

a charging step of encapsulating water and a water-permeable vesselcharged with the cellulosic biomass into the pressure vessel;

a heating-up step of hermetically closing the pressure vessel andheating up the pressure vessel;

a hydrolyzing step of hydrolyzing cellulose and/or hemicellulosecontained in the cellulosic biomass into saccharides by an oxidativepower of high-temperature and high-pressure water;

a temperature lowering step of flash-evaporating high-temperature andhigh-pressure water contained in the pressure vessel to lower thetemperature thereof; and

a discharging step of removing a residue of the cellulosic biomass outof the pressure vessel, wherein:

while any one of the plural pressure vessels performs the charging step,any one of the other pressure vessels performs the discharging step soas to allow heat exchange to occur between water to be charged into thepressure vessel performing the charging step and high-temperature waterto be discharged from the pressure vessel performing the dischargingstep; and

while any one of the plural pressure vessels performs the heating-upstep, any one of the other pressure vessels performs the temperaturelowering step and allows heat recovery to be made by supplying flashvapor discharged from the pressure vessel performing the temperaturelowering step to the pressure vessel performing the heating-up step(claim 24).

In hydrolyzing cellulose or hemicellulose into saccharides by usinghigh-temperature and high-pressure water in a subcritical condition, thecellulosic biomass is charged into the water-permeable vessel havingperforations, apertures or the like for allowing water to move from theexterior to the interior of the water-permeable vessel and vice versaand then the water-permeable vessel and water are encapsulated into eachpressure vessel (compressive and dense encapsulation). By so doing, thevessels and associated piping can be prevented from being contaminatedwith fine residue of slurry.

In cases where equal time is required to complete respective of all theaforementioned five steps, the number of the pressure vessels used ispreferably a multiple of five (claims 3 and 25). With this feature, thesequential steps can be performed smoothly while performing heatrecovery twice.

In cases where equal time is required to complete respective of all thefour steps other than the hydrolyzing step and the time required tocomplete the hydrolyzing step is n times (where n is a natural number)as long as the time required to complete respective of all the otherfour steps, the number of the pressure vessels used is preferably amultiple of (4+n) (claims 4 and 26). Where the time required to completethe hydrolyzing step is n times as long as that required to complete anyother step, the number of pressure vessels to perform the hydrolyzingstep is preferably n times as large as the number of pressure vessels toperform the other steps. With this feature, the sequential steps can beperformed smoothly while performing heat recovery twice.

When the hydrolyzing step is performed at a temperature of not lowerthan 140° C. and not higher than 180° C., hemicellulose can behydrolyzed into saccharides (mainly including C5 monosaccharides)(claims 5 and 6). A biomass containing a large amount of hemicelluloseis preferably processed under relatively moderate conditions becausehigh-temperature processing causes C5 monosaccharides and the like todegrade into organic acids and the like.

Thereafter, the slurry resulting from the discharging step is subjectedto solid-liquid separation; a solid content produced after elution ofhydrolyzed hemicellulose to the solvent side is separated out for use asa fresh raw slurry; the raw slurry is subjected to the charging stepagain; and the hydrolyzing step is performed at a temperature of notlower than 240° C. and not higher than 280° C. By so doing, cellulosecan be hydrolyzed into saccharides (mainly including C6 monosaccharides)(claim 7).

Alternatively, by subjecting the water-permeable vessel having beensubjected to the discharge step to the charging step again andperforming the hydrolyzing step at a temperature of not lower than 240°C. and not higher than 280° C., it is possible to hydrolyze celluloseinto saccharides (claim 8).

Hemicellulose contained in the biomass is first hydrolyzed intosaccharides at a temperature of not lower than 140° C. and not higherthan 180° C. and then the biomass is subjected to solid-liquidseparation. By so doing, cellulose can be separated out as a solid. Aslurry comprising the cellulose thus obtained is subjected to thecharging step and then to the hydrolyzing step at a temperature of notlower than 240° C. and not higher than 280° C. By so doing, thecellulose can be hydrolyzed into saccharides. This process is effectivefor a biomass containing cellulose and hemicellulose in substantiallyequal amounts.

When the hydrolyzing step is performed at a temperature of not lowerthan 240° C. and not higher than 280° C., cellulose can be hydrolyzedinto saccharides (mainly including C6 monosaccharides) (claim 9). In thecase of a biomass having a high cellulose content, a process forhydrolyzing only cellulose into saccharides at a relatively hightemperature is more effective because the necessity to take degradationof hemicellulose into consideration is low.

Preferably, the charging step includes addition of ethanol in an amountof not less than 2 mol % and not more than 10 mol % to the raw slurry orto water to be encapsulated in the pressure vessel step (claims 10 and11). The addition of a small amount of ethanol to the raw slurry causesthe reaction rate of hydrolysis of cellulose and/or hemicellulose intosaccharides by subcritical water to be lowered. Thus, the celluloseand/or hemicellulose hydrolysis time in the hydrolyzing step can beadjusted so as to facilitate inhibition of degradation into organicacids and the like, thereby raising the yield.

The present invention is also directed to a method of hydrolyticsaccharification of a cellulosic biomass with use of plural pressurevessels, the method comprising a discharging and charging step, aheating-up step, a hydrolyzing step, and a temperature lowering step,which are performed sequentially by each of the pressure vessels,wherein:

the discharging and charging step is a step of removing a slurry out ofeach of the pressure vessel after the temperature lowering step andcharging a slurry prepared by grinding the cellulosic biomass and mixingthe cellulosic biomass thus ground with water into the same pressurevessel;

the heating-up step is a step of hermetically closing the pressurevessel and heating up the pressure vessel;

the hydrolyzing step is a step of hydrolyzing cellulose and/orhemicellulose contained in the cellulosic biomass into saccharides by anoxidative power of high-temperature and high-pressure water;

the temperature lowering step is a step of flash-evaporating thehigh-temperature and high-pressure slurry contained in the pressurevessel to lower the temperature thereof; and

while any one of the plural pressure vessels performs the heating-upstep, any one of the other pressure vessels performs the temperaturelowering step and allows heat recovery to be made by supplying flashvapor discharged from the pressure vessel performing the temperaturelowering step to the pressure vessel performing the heating-up step(claim 12).

The present invention is also directed to a system for hydrolyticsaccharification of a cellulosic biomass, comprising plural pressurevessels each configured to perform sequential steps including:

a discharging and charging step of removing a high-temperature slurryout of the pressure vessel after a temperature lowering step andcharging a slurry prepared by grinding the cellulosic biomass and thenmixing the cellulosic biomass thus ground with water into the samepressure vessel;

a heating-up step of hermetically closing the pressure vessel andheating up the pressure vessel;

a hydrolyzing step of hydrolyzing cellulose and/or hemicellulosecontained in the cellulosic biomass into saccharides by an oxidativepower of high-temperature and high-pressure water; and

the temperature lowering step of flash-evaporating the high-temperatureand high-pressure slurry contained in the pressure vessel to lower thetemperature thereof, wherein

while any one of the plural pressure vessels performs the heating-upstep, any one of the other pressure vessels performs the temperaturelowering step and allows heat recovery to be made by supplying flashvapor discharged from the pressure vessel performing the temperaturelowering step to the pressure vessel performing the heating-up step(claim 27).

The present invention is also directed to a method of hydrolyticsaccharification of a cellulosic biomass with use of plural pressurevessels, the method comprising a discharging and charging step, aheating-up step, a hydrolyzing step, and a temperature lowering step,which are performed sequentially by each of the pressure vessels,wherein:

the discharging and charging step is a step of removing a cellulosicbiomass residue out of each of the pressure vessels after thetemperature lowering step and encapsulating water and a water-permeablevessel charged with the cellulosic biomass into the same pressurevessel;

the heating-up step is a step of hermetically closing the pressurevessel and heating up the pressure vessel;

the hydrolyzing step is a step of hydrolyzing cellulose and/orhemicellulose contained in the biomass into saccharides by an oxidativepower of high-temperature and high-pressure water;

the temperature lowering step is a step of flash-evaporatinghigh-temperature and high-pressure water contained in the pressurevessel to lower the temperature thereof; and

while any one of the plural pressure vessels performs the heating-upstep, any one of the other pressure vessels performs the temperaturelowering step and allows heat recovery to be made by supplying flashvapor discharged from the pressure vessel performing the temperaturelowering step to the pressure vessel performing the heating-up step(claim 13).

The present invention is also directed to a system for hydrolyticsaccarification of a cellulosic biomass, comprising plural pressurevessels each configured to perform sequential steps including:

a discharging and charging step of removing a cellulosic biomass residueout of the pressure vessel after a temperature lowering step andencapsulating water and a water-permeable vessel charged with thecellulosic biomass into the pressure vessel;

a heating-up step of hermetically closing the pressure vessel andheating up the pressure vessel;

a hydrolyzing step of hydrolyzing cellulose and/or hemicellulosecontained in the cellulosic biomass into saccharides by an oxidativepower of high-temperature and high-pressure water; and

the temperature lowering step of flash-evaporating high-temperature andhigh-pressure water contained in the pressure vessel to lower thetemperature thereof, wherein

while any one of the plural pressure vessels performs the heating-upstep, any one of the other pressure vessels performs the temperaturelowering step and allows heat recovery to be made by supplying flashvapor discharged from the pressure vessel performing the temperaturelowering step to the pressure vessel performing the heating-up step(claim 28).

By thus performing the discharging step and the charging step in onepressure vessel, it is possible to reduce the total number of processsteps to four and the total number of pressure vessels used to four (ora multiple of four) and shorten the processing time. For this reason,this method and system has the advantage of improving the productioncapacity. With the hydrolytic saccharification method and system havingfour steps in total according to the present invention, heat exchangebetween the high-temperature slurry to be discharged from each vesseland the slurry (raw slurry) to be charged into the same pressure vesselis possible in the discharging and charging step.

Similarly, with the hydrolytic saccharification method and system havingfour process steps in total according to the present invention, heatexchange between high-temperature water be discharged from each vesseland water to be charged into the same pressure vessel is possible in thedischarging and charging step.

In cases where equal time is required to complete respective of all theaforementioned four steps, the number of pressure vessels used ispreferably a multiple of four (claims 14 and 29). With this feature, thesequential steps can be performed smoothly while performing heatrecovery twice.

In cases where equal time is required to complete respective of all thethree steps other than the hydrolyzing step and the time required tocomplete the hydrolyzing step is n times (where n is a natural number)as long as the time required to complete each of the other three steps,the number of pressure vessels used is preferably a multiple of (3+n)(claims 15 and 30). In cases where the time required to complete thehydrolyzing step is n times as long as that required to complete anyother step, the number of pressure vessels to perform the hydrolyzingstep is preferably n times as large as the number of pressure vessels toperform the other steps. With this feature, the sequential steps can beperformed smoothly while performing heat recovery twice.

When the hydrolyzing step is performed at a temperature of not lowerthan 140° C. and not higher than 180° C., the hydrolyticsaccharification method including four process steps in total is alsocapable of hydrolyzing hemicellulose into saccharides (mainly includingC5 monosaccharides) (claims 16 and 17).

The slurry resulting from the discharging and charging step is subjectedto solid-liquid separation; a solid content produced after elution ofhydrolyzed hemicellulose to the solvent side is separated out for use asa fresh raw slurry; the raw slurry is charged into the same pressurevessel again in the discharging and charging step; and the hydrolyzingstep is performed at a temperature of not lower than 240° C. and nothigher than 280° C. By so doing, cellulose can be hydrolyzed intosaccharides (mainly including C6 monosaccharides) (claim 18).

Alternatively, by subjecting the water-permeable vessel having beensubjected to the discharge step to the charging step again andperforming the hydrolyzing step at a temperature of not lower than 240°C. and not higher than 280° C., it is possible to hydrolyze celluloseinto saccharides (claim 19).

When the hydrolyzing step is performed at a temperature of not lowerthan 240° C. and not higher than 280° C., cellulose can be hydrolyzedinto saccharides (mainly including C6 monosaccharides) (claim 20).

Preferably, the discharging and charging step includes addition ofethanol in an amount of not less than 2 mol % and not more than 10 mol %to the raw slurry or to water to be encapsulated into each pressurevessel (claims 21 and 22). The reasons that the aforementionedtemperature conditions and the addition of ethanol are preferable are asstated above for the charging step of the hydrolytic saccharificationmethod including five process steps in total.

Ethanol added to the raw slurry is mostly transferred to flash vapor inthe temperature lowering step and then collected into the slurry inanother pressure vessel performing the heating-up step. The aqueoussolution containing saccharides, which is removed out of each pressurevessel by the discharging step, is subjected to ethanol fermentation andthereby converted to bioethanol. If ethanol remains in the initial phaseof ethanol fermentation, fermentation by yeast is inhibited by suchresidual ethanol. The inventions according to claims 10, 11, 21 and 22have the feature that ethanol fermentation is difficult to inhibitbecause the method can reduce the amount of ethanol in the slurrycontaining cellulose and/or hemicellulose which is obtained after thedischarging step while keeping a desired ethanol concentration in thehydrolyzing step.

As disclosed in patent document 4 or 5, when the medium comprisingalcohol or the like as a major component is brought into its subcriticalcondition, the internal pressure of the pressure vessel becomes as highas or higher than 12 MPa at 280° C. for example. With the inventionaccording to claim 7, in contrast, the internal pressure of the pressurevessel reaches no more than about 7.5 to about 9.7 MPa at 280° C., whichthe same temperature. Thus, the method according to this invention iscapable of saving the pressurizing energy while allowing the pressureresistance of the pressure vessel to lower, thereby offering aneconomical merit.

The foregoing and other objects, features and attendant advantages ofthe present invention will become more apparent from the reading of thefollowing detailed description of the invention in conjunction with theaccompanying drawings.

Advantage of the Invention

According to the present invention, cellulose and/or hemicellulosecontained in a cellulosic biomass can be hydrolyzed into saccharides ina high yield at a low cost with use of plural pressure vessels. Also,the present invention can save the required calorie by about 60% andhence has a very excellent economical merit because waste heat can beeasily recovered from a pressure vessel performing another step andutilized for preheating to a suitable temperature for hydrolyticsaccharification reaction.

By charging a cellulosic biomass into the water-permeable vessel andencapsulating the water-permeable vessel and water into each pressurevessel, it is possible to prevent piping and the like from being stainedas well as to improve the operating efficiency further.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart illustrating a procedure for operating a hydrolyticsaccharification system according to embodiment 1;

FIG. 2 is a time schedule chart for operating the hydrolyticsaccharification system of embodiment 1 as a sequencing batch system;

FIG. 3 is a time schedule chart for operating a hydrolyticsaccharification system of embodiment 2 as a sequencing batch system;

FIG. 4 is a graph plotting the relationship between the reaction time ofhydrolytic saccharification of a biomass and the yield of saccharides(%);

FIG. 5 is a time schedule chart for operating a hydrolyticsaccharification system of embodiment 3 as a sequencing batch system;and

FIG. 6 is a view illustrating an example in which dried bagasse iscompressively and densely charged into a water-permeable vesselaccording to embodiment 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withappropriate reference to the drawings. It is to be noted that thepresent invention is not limited to the embodiments described below.

Embodiment 1

Referring to FIG. 1, description will be made of a procedure foroperating a hydrolytic saccharification system configured to performfive process steps in total and use five pressure vessels according toembodiment 1.

First, a cellulosic biomass (for example, a vegetation biomasscomprising bagasse, sugar beet residue, straws or the like) is ground tosizes of not more than several millimeters and then mixed with water ora dilute ethanol aqueous solution (2 to 10 mol %) to prepare a slurryhaving a solid matter concentration of about 30%. The slurry thusobtained (raw slurry) is charged into pressure vessel No. 1, as shown inFIG. 1( a) (charging step). Since there is no thermal energy releasedfrom any other pressure vessel at the time the hydrolyticsaccharification system starts operating, the raw slurry cannot bepreheated by heat exchange.

Pressure vessels Nos. 1 to 5 each repeatedly perform the sequence ofprocess steps: charging step→heating-up step→hydrolyzingstep→temperature lowering step→discharging step, and four pressurevessels Nos. 2 to 5 each operate with a time lag corresponding to oneprocess step. In the case of FIGS. 1( a) to 1(e), when pressure vesselNo. 1 is at the charging step, pressure vessels Nos. 2 to 5 are at thedischarging step, temperature lowering step, hydrolyzing step andheating-up step, respectively.

In FIGS. 1( a) to 1(e), the terms “preheat and charge”, “preheat andheat-up”, “heat-up”, “flash” and “drainage” represent the charging step,heating-up step, hydrolyzing step, temperature lowering step anddischarging step, respectively.

In cases where the hydrolytic saccharification system is already inoperation and the second or later charging step is to be performed bypressure vessel No. 1, heat exchange is allowed to occur between aslurry (containing saccharides) to be discharged (or drained) frompressure vessel No. 2 at the discharge step and the raw slurry to becharged into pressure vessel No. 1, thereby preheating the raw slurry.

Subsequently, pressure vessel No. 1 is closed hermetically (heating-upstep). At that time pressure vessel No. 4 is at the temperature loweringstep as shown in FIG. 1( b). For this reason, high-temperature gaspresent in an upper portion of pressure vessel No. 4 is supplied asflash vapor to pressure vessel No. 1 in order to recover heat. (Asdescribed above, flash vapor is preferably supplied into the aqueoussolution contained in the pressure vessel.) As a result, the temperatureof the slurry contained in pressure vessel No. 1 is raised further,whereby the energy required to bring the slurry into its subcriticalcondition can be saved.

Subsequently, the interior of pressure vessel No. 1 is heated using aheat source, such as high-temperature steam, to bring the slurry intoits subcritical condition, as shown in FIG. 1( c) (hydrolyzing step).Preferably, ethanol is previously added to the raw slurry to aconcentration of not less than 2 mol % and not more than 10 mol %. Theaddition of ethanol allows the hydrolysis reaction rate to be lowered,thereby making it easy to control the hydrolysis reaction of celluloseor hemicellulose in the hydrolyzing step.

The “hydrolyzing step”, as used in the present invention, is meant toinclude not only the time during which the slurry is in the subcriticalcondition but also the time required to heat the slurry having beenraised in temperature by the heating-up step until the slurry is broughtinto the subcritical condition.

If ethanol is added to the raw slurry to a concentration of more than 10mol %, the hydrolysis time becomes longer than necessary while at thesame time the pressure vessel needs to have a higher pressureresistance. In addition, the slurry discharged (or drained) by thedischarging step contains a high concentration of residual ethanol. Forthese reasons, the addition of too much ethanol impairs the practicalvalue of the invention.

Subsequently, pressure vessel No. 1 having passed a proper hydrolysistime is connected to pressure vessel No. 3 at the preheating step inorder to supply, as flash vapor, the high-temperature slurry present ina lower portion of pressure vessel No. 1 into pressure vessel No. 3, asshown in FIG. 1( d). By so doing, the interior of pressure vessel No. 1is rapidly cooled to a temperature below the hydrolytic saccharificationtemperature, thereby making it possible to stop degradation reaction ofsaccharides into organic acids or the like. At the same time, thetemperature of the slurry in pressure vessel No. 3 is raised.

In order for hemicellulose contained in the biomass to be hydrolyticallysaccharificated in the hydrolyzing step, the temperature of the slurryis adjusted to within the temperature range of from 140° C. to 180° C.which allows only hemicellulose to be hydrolytically saccharificated,without being raised to within the temperature range (240° C. to 280°C.) which allows cellulose to be hydrolytically saccharificated. On theother hand, in order for cellulose contained in the biomass to behydrolytically saccharificated, the temperature of the slurry is raisedto within the temperature range (240° C. to 280° C.) which allowscellulose to be hydrolytically saccharificated.

Subsequently, pressure vessel No. 1 of which the temperature has loweredand of which the pressure has lowered to a normal pressure or a pressureclose to the normal pressure is opened and the slurry containingsaccharides is discharged (or drained) therefrom, as shown in FIG. 1( e)(discharging step). In the case of the slurry having been subjected to atemperature of from 240° C. to 280° C. in the hydrolyzing step, thetemperature of the slurry in the discharging step is about 110° C. toabout 150° C. For this reason, heat exchange is allowed to occur betweenthe slurry in pressure vessel No. 1 at the discharging step and theslurry to be charged into pressure vessel No. 5. By so doing, it ispossible to preheat the slurry to be charged into pressure vessel No. 5as well as to cool the slurry to be removed out of pressure vessel No.1.

While description has been made mainly of the operating procedure forpressure vessel No. 1 with reference to FIGS. 1( a) to 1(e), pressurevessels Nos. 2 to 5 are each operated according to the same procedure.With respect to the pressure vessels other than pressure vessel No. 1,the waste heat recovery (i.e., heat exchange) operations using flashvapor and high-temperature slurry are partly omitted from FIGS. 1( a) to(e). However, it is needless to say that waste heat recovery (i.e., heatexchange) is performed for each of these pressure vessels in the samemanner as for pressure vessel No. 1.

Saccharides and residual solid content coexist in the slurry discharged(or drained) by the discharging step and cooled by heat exchange. Wherethe hydrolyzing step temperature is within the range of from 140° C. to180° C., the residual solid content comprises cellulose and lignin asmajor components. Where the hydrolyzing step temperature is within therange of from 240° C. to 280° C., the residual solid content compriseslignin as a major component.

After the residual solid content of the slurry has been removed away bysolid-liquid separation, the resulting liquid is subjected to ethanolfermentation utilizing the fermentation action and the like of yeast,thus giving bioethanol. Since such an ethanol fermentation technique iswell-known, description thereof is omitted herein. Saccharides obtainedby the present invention can be converted to bioethanol by a knownfermentation process other than yeast fermentation.

Referring to FIG. 2, description will be made of a time schedule foroperating the hydrolytic saccharification system using the five pressurevessels shown in FIGS. 1( a) to 1(b) as a sequencing batch system. InFIG. 2, the time required to complete each process step is five minutes.

Initially, pressure vessel No. 1 performs the charging step and,subsequently, pressure vessels Nos. 2 to 5 perform the charging stepsequentially with a time lag of five minutes from one pressure vessel tothe next one. Each pressure vessel repeats the five sequential steps:[C]→[PH]→[GL]→[F]→[DC] and, accordingly, one cycle of the hydrolyticsaccharification process for a cellulosic biomass is 5 min×5 steps=25minutes. Pressure vessels Nos. 1 to 5 perform this cycle sequentiallywith a time lag of five minutes from one pressure vessel to the nextone.

Flashing vapor contained in pressure vessel No. 1 at the temperaturelowering step is supplied to pressure vessel No. 2 at the heating-upstep, thus making heat recovery. Likewise, flashing vapor contained ineach of pressure vessels Nos. 2 to 5 at the temperature lowering step issupplied to a respective one of pressure vessels Nos. 3, 4, 5 and 1,thus making heat recovery.

The slurry to be discharged (or drained) from pressure vessel No. 1 atthe discharging step exchanges heat with the slurry to be charged intopressure vessel No. 5 at the charging step. Likewise, thehigh-temperature slurry contained in each of pressure vessels Nos. 2 to5 at the discharge step exchanges heat with the slurry to be chargedinto a respective one of pressure vessels Nos. 1 to 4 at the chargingstep.

Such a sequencing batch system makes it possible to hydrolyticallysaccharificate a biomass in a short time with the required energy saved.

Embodiment 2

Referring to FIG. 3, description will be made of a time schedule foroperating a hydrolytic saccharification system as a sequencing batchsystem, the hydrolytic saccharification system being configured toperform four steps in total and use four pressure vessels eachconfigured to perform the discharging step and the charging step inparallel as a discharging and charging step in a steady operation. InFIG. 3, the time required to complete each step is five minutes.

Initially, pressure vessel No. 1 performs the first charging step Coand, subsequently, pressure vessels Nos. 2 to 4 perform the firstcharging step Co sequentially with a time lag of five minutes from onepressure vessel to the next one. When the system starts operating, thesystem performs the same charging step as does the hydrolyticsaccharification system shown in FIG. 1. For this reason, thedischarging and charging step performed first is referred to as “firstcharging step Co” in FIG. 3. In steady operation, each pressure vesselrepeats the four sequential steps: [C]→[PH]→[GL]→[F] and, accordingly,one cycle of the hydrolytic saccharification process for a cellulosicbiomass is 5 min×4 steps=25 minutes. Pressure vessels Nos. 1 to 4perform this cycle sequentially with a time lag of five minutes from onepressure vessel to the next one.

Flashing vapor contained in pressure vessel No. 1 at the temperaturelowering step is supplied to pressure vessel No. 2 at the heating-upstep, thus making heat recovery. Likewise, flashing vapor contained ineach of pressure vessels Nos. 2 to 4 at the temperature lowering step issupplied to a respective one of pressure vessels Nos. 3 to 5 at theheating-up step, thus making heat recovery.

The slurry is removed out of pressure vessel No. 1 at the dischargingand charging step after the temperature lowering step and then a rawslurry is charged into the same pressure vessel. That is, pressurevessel No. 1 having completed the temperature lowering step performs thedischarging step and the charging step in parallel. When the temperatureof the slurry to be discharged is sufficiently high, heat exchange withthe raw slurry to be charged may be made.

In terminating the operation, pressure vessel No. 1 having completed thelast temperature lowering step performs the last discharging step Cxand, subsequently, pressure vessels Nos. 2 to 4 perform the lastdischarging step Cx sequentially with a time lag of five minutes fromone pressure vessel to the next one. In terminating the operation of thesystem, the system performs the same discharging step as does thehydrolytic saccharification system shown in FIG. 1. For this reason, thedischarging and charging step performed last is referred to as “the lastdischarging step Cx” in FIG. 3.

This sequencing batch system is capable of achieving continuoushydrolytic saccharification in a shorter time with fewer pressurevessels than the hydrolytic saccharification system shown in FIGS. 1 and2.

Effect of the Addition of Ethanol in the Hydrolyzing Step

Effect of the addition of ethanol on hydrolytic saccharification ofreagent cellulose under the subcritical condition was studied with thereagent cellulose used as a biomass. FIG. 4 shows the result of anexperiment in which pure water and 5 wt % (2 mol %) ethanol aqueoussolution, which were at the same temperature of 280° C., were eachpassed through the above-noted cellulose.

FIG. 4 shows the relationship between the reaction time and the yield ofsaccharides (%). The addition of ethanol was found to have substantiallyno effect on the maximum yield of saccharides. With respect to thesaccharide production rate and the hydrolisis rate, however, they wereapparently lowered by the addition of ethanol. For example, the timerequired to reach the maximum yield was increased about three times (0.7min→2.0 min) by the addition of ethanol.

It is difficult for an industrial-scale system to control the reactiontime under the subcritical condition to the second. For this reason, theaddition of ethanol to a raw slurry was confirmed effective in raisingthe yield of saccharides.

Embodiment 3

Referring to FIG. 5, description will be made of a time schedule foroperating a hydrolytic saccharification system as a sequencing batchsystem, the hydrolytic saccharification system being configured toperform five steps in total and use eight pressure vessels. This systemis adapted to cases where a cellulosic biomass is difficult tohydrolytically saccharificate under the subcritical condition and,hence, the hydrolyzing step cannot but be performed for a longer timethan the other four steps. In FIG. 5, the time required to complete thehydrolyzing step is 20 minutes and that required to complete any otherstep is five minutes.

Initially, pressure vessel No. 1 performs the charging step and,subsequently, pressure vessels Nos. 2 to 8 perform the charging stepsequentially with a time lag of five minutes from one pressure vessel tothe next one. Each pressure vessel repeats the five sequential steps:[C]→[PH]→[GL]→[F]→[DC]. Here, the time required to complete the step ofhydrolyzing a cellulosic biomass into saccharides is 20 minutes and,accordingly, one cycle of the hydrolytic saccharification process is (5min×4 steps)+(20 min×1 step)=40 minutes. Pressure vessels Nos. 1 to 8perform this cycle sequentially with a time lag of five minutes from onepressure vessel to the next one.

With the sequencing batch system shown in FIG. 5, the time required tocomplete the hydrolyzing step is four times as long as that required tocomplete any other process step. Therefore, if five pressure vessels,the number of which corresponds to the five process steps, are used, thethermal energy of flash vapor and that of high-temperature slurry cannotbe recovered unless each of the process steps other than the hydrolyzingstep takes 20 minutes as does the hydrolyzing step. For this reason, theprocessing time would be very long. In view of such an inconvenience,the hydrolytic saccharification system according to the presentembodiment uses eight pressure vessels to realize effective heatrecovery while taking five minutes for any other process step than thehydrolyzing step as does the foregoing system and 20 minutes for thehydrolyzing step.

When pressure vessel No. 1 is at the temperature lowering step, flashingvapor contained in pressure vessel No. 1 is supplied to pressure vesselNo. 6 at the heating-up step. Likewise, flashing vapor contained in eachof pressure vessels Nos. 2 to 8 at the temperature lowering step issupplied to a respective one of pressure vessels Nos. 7, 8, 1, 2, 3, 4and 5, thus making heat recovery.

The high-temperature slurry to be discharged (or drained) from pressurevessel No. 1 at the discharging step exchanges heat with the slurry tobe charged into pressure vessel No. 8 at the charging step. Likewise,the high-temperature slurry to be discharged from each of pressurevessels Nos. 2 to 8 at the discharge step exchanges heat with the slurryto be charged into a respective one of pressure vessels Nos. 1 to 7.

In cases where equal time is required to complete respective of the foursteps other than the hydrolyzing step and the time required to completethe hydrolyzing step is n times (where n is a natural number; n is fourin this example) as long as the time required to complete each of theother four steps, the number of pressure vessels used is preferably amultiple of (4+n). The system thus arranged a sequencing batch system iscapable of achieving continuous hydrolytic saccharification of acellulosic biomass in a short time with the required energy saved, likeembodiment 1.

While embodiment 3 uses eight pressure vessels, the hydrolyticsaccharification system, when comprising two sequencing bath systems,may use 16 pressure vessels in total. The hydrolytic saccharificationsystem configured to perform four process steps in total may be operatedin a similar manner as above.

Embodiment 4

With respect to the foregoing embodiments 1 to 3, description has beendirected to the cases where a cellulosic biomass is ground and thenmixed with water to prepare a slurry, which is then charged into apressure vessel in the charging step or the discharging and chargingstep. In the charging step or the discharging and charging stepaccording to the present invention, however, a cellulosic biomass neednot necessarily be slurried. Hydrolysis saccharification of a cellulosicbiomass can be achieved also by such a charging step or discharging andcharging step which includes: charging a cellulosic biomass, such asbagasse, into a water-permeable vessel having perforations, apertures orthe like for allowing water to move from the exterior to the interior ofthe water-permeable vessel and vice versa; and encapsulating thewater-permeable vessel and water into each pressure vessel (compressiveand dense encapsulation).

Though there is no limitation on the material of the water-permeablevessel as long as the material can withstand elevated temperatures inthe pressure vessel, the material is preferably stainless steel and alike material having a high endurance. Also, there is no limitation onthe shape of the water-permeable vessel; for example, arectangular-parallelepiped shape, a cylindrical shape or the like may beappropriately selected for the water-permeable vessel. However, the sameshape as the internal shape (cylindrical shape) of each pressure vesselis preferable in view of its high volumetric efficiency. Any means forensuring the water-permeability may be employed without any particularlimitation as long as the water-permeable vessel allows water to movefrom the exterior to the interior of the water-permeable vessel and viceversa; for example, the water-permeable vessel may be partially orentirely reticulated; the water-permeable vessel may be formed withslits or circular perforations; or the water-permeable vessel may haveopen top.

FIG. 6 illustrates an example in which dried bagasse as a cellulosicbiomass is charged into the water-permeable vessel. In this figure, thewater-permeable vessel to be charged with bagasse has a cylindricalshape (with open top) having a bottom surface and a peripheral surface,which are formed with multiple perforations. In this case there is noneed to grind the dried bagasse. The dried bagasse may be used with itslength left as it is or cut to an appropriate length.

After charging, it is preferable to compress the dried bagasse withinthe water-permeable vessel from above by means of a pressing machine orthe like. The dried baggase in a previously compressed condition may becharged into the water-permeable vessel. The dried bagasse, which has abulk specific gravity of about 5 to about 10 kg/m3 before compression,can be compressed to a bulk specific gravity of not less than 50 kg/m3.The dried bagasse in this compressed condition is encapsulated into eachpressure vessel and then water is poured into the pressure vessel tocapacity. By so doing, the interior of the pressure vessel has a solidmatter concentration of about several %, which is the same level ofsolid matter concentration as the slurry. Therefore, the pressure vesselhas substantially the same volumetric efficiency as with the driedbagasse in the form of slurry.

In compressing dried bagasse within the water-permeable vessel, it ispreferable that the water-permeable vessel is compressively and denselycharged with dried bagasse as much as possible by repeating theintroduction of dried bagasse into the water-permeable vessel and thepressing operation. The pressing operation may be performed only once aslong as a sufficient amount of dried bagasse can be compressively anddensely charged into the water-permeable vessel.

The bulk specific gravity of a cellulosic biomass, such as driedbaggase, is preferably adjusted to a value of not less than 50 kg/m3 andnot more than 300 kg/m3, more preferably not less than 100 kg/m3 and notmore than 200 kg/m3, before encapsulation into the pressure vessel. Ifthe bulk specific gravity of the cellulosic biomass is too low, thesolid matter concentration becomes lower than that of the cellulosicbiomass in the form of slurry, which results in a lowered volumetricefficiency. On the other hand, if the bulk specific gravity of thecellulosic biomass is too high, it is difficult for water to penetrateinto the cellulosic biomass and, hence, the hydrolysis reaction of thecellulosic biomass occurs with difficulty.

In slurrying a cellulosic biomass such as dried bagasse, the energyrequired to pulverize the cellulosic biomass is about 0.5 to 2 kW per 1kg of the raw material. Such a pulverizing operation is eliminated inthe present embodiment. Even if grinding is necessary, pulverization isnot required. The amount of work required to pretreat the cellulosicbiomass is reduced to 1/10 to ½.

In charging the cellulosic biomass in the form of slurry into a pressurevessel, it is required that the solid matter concentration be lowered orthe cellulosic biomass be pulverized in order to prevent the piping frombeing clogged. The cellulosic biomass has a relatively high watercontent. For this reason, even when the solid matter concentration ofthe slurry is about 10% with the water content of the cellulosic biomasstaken into consideration, the flowability of the slurry is low. However,by encapsulating the water-permeable vessel charged with the cellulosicbiomass into the pressure vessel together with water, the solid matterconcentration within the pressure vessel can be made substantially equalto that of the slurry, as described above.

With the cellulosic biomass in the form of slurry, solid matter issometimes deposited on the inner wall of the piping as well as on theinner wall of the pressure vessel and remains thereon as residual solidmatter. Such residual solid matter not only causes the volumetricefficiency of each of the piping and the pressure vessel but also mixes,as reacted fine powder, into unreacted slurry. Therefore, such residualsolid matter causes the frequency of cleaning to increase. However, sucha problem will not arise by virtue of the step of encapsulating thewater-permeable vessel charged with the cellulosic biomass into thepressure vessel together with water, followed by heating because onlywater passes through the piping with the cellulosic biomass left withinthe water-permeable vessel.

Further, in cases where the cellulosic biomass is heated at atemperature of not lower than 140° C. and not higher than 180° C. tohydrolyze hemicellulose into saccharides and then the residual solidmatter is heated at a temperature of not lower than 240° C. and nothigher than 280° C. to hydrolyze cellulose into saccharides, it isrequired that the solid content obtained after the hydrolysis ofhemicellulose be separated out by solid-liquid separation and then mixedwith water again to form a slurry when the charging step or thedischarging and charging step includes charging the cellulosic biomassin the form of slurry into the pressure vessel. However, with theprocess of encapsulating the water-permeable vessel charged with thecellulosic biomass into the pressure vessel together with water and thenheating the pressure vessel, there are advantages that it is sufficientto discharge water containing saccharides and that the water-permeablevessel serves also as the means for solid-liquid separation. Bycollecting water containing saccharides that remains together with thebiomass residue in the water-permeable vessel by washing the biomassresidue, it is possible to collect saccharides more efficiently.

In cases where the water-permeable vessel charged with the cellulosicbiomass is encapsulated into the pressure vessel together with water inthe charging step or the discharging and charging step, the dischargingstep or the discharging and charging step includes: discharginghigh-temperature water containing saccharides; removing thewater-permeable vessel out of the pressure vessel; and removing a solidresidue (which is a residual solid matter left after hydrolysis ofcellulose and/or hemicellulose contained in the cellulosic biomass andcomprising lignin and an ash content as major components), followed bydisposal.

Since this residue can be utilized as a fuel for heating the interior ofthe pressure vessel, the present embodiment, according to which thesolid matter concentration within the pressure vessel can be raised and,hence, the amount of residue removed out of the pressure vessel can beincreased, is capable of suppressing the amount of fuel to be used, suchas petrol.

In the temperature lowering step, high-temperature water contained inthe pressure vessel is flash-evaporated to exchange heat with water tobe charged into the pressure vessel performing the charging step. Otherfeatures are similar to the corresponding features of the method andsystem in which the cellulosic biomass in the form of slurry is chargedby the charging step or the discharging and charging step.

For example, in the case of the charging step in which the cellulosicbiomass is charged into the water-permeable vessel and then encapsulatedinto the pressure vessel together with water, the “water andwater-permeable vessel charged with the cellulosic biomass” isequivalent to the “raw slurry” appearing in FIG. 1 illustrating theprocedure for operating the hydrolytic saccharification system ofembodiment 1.

It will be apparent from the foregoing description that manyimprovements and other embodiments of the present invention may occur tothose skilled in the art. Therefore, the foregoing description should beconstrued as an illustration only and is provided for the purpose ofteaching the best mode for carrying out the present invention to thoseskilled in the art. The details of the structure and/or the function ofthe present invention can be modified substantially without departingfrom the spirit of the present invention.

INDUSTRIAL APPLICABILITY

The present invention is useful as a method and system for hydrolyzing acellulosic biomass into saccharides, to be applied in industrial fieldssuch as the bioindustry and energy industry.

1.-30. (canceled)
 31. A batch wise method of hydrolytic saccharificationof a cellulosic biomass with use of plural pressure vessels, the methodcomprising a charging step, a heating up step, a hydrolyzing step, atemperature lowering step, and a discharging step, which are performedsequentially by each of said pressure vessels, wherein: said chargingstep is a step of charging a slurry prepared by grinding said cellulosicbiomass and then mixing said cellulosic biomass thus ground with waterinto each of said pressure vessels; said heating up step is a step ofhermetically closing the pressure vessel and heating up said slurry;said hydrolyzing step is a step of hydrolyzing cellulose and/orhemicellulose contained in said cellulosic biomass into saccharides byan oxidative power of high temperature and high pressure water; saidtemperature lowering step is a step of flash evaporating the hightemperature and high pressure slurry contained in the pressure vessel tolower the temperature thereof; said discharging step is a step ofremoving the slurry out of the pressure vessel; equal time is requiredto complete respective of all the four steps other than said hydrolyzingstep; the time required to complete said hydrolyzing step is n times(where n is a natural number) as long as the time required to completeeach of the other four steps; and the number of the pressure vesselsused is a multiple of (4+n). while any one of said plural pressurevessels performs said charging step, any one of the other pressurevessels performs said discharging step so as to allow heat exchange tooccur between the slurry to be charged into the pressure vesselperforming the charging step and the slurry to be discharged from thepressure vessel performing said discharging step; and while any one ofthe said plural pressure vessels performs said heating up step, any oneof the other pressure vessels performs said temperature lowering stepand allows heat recovery to be made by supplying flash vapor dischargedfrom the pressure vessel performing the temperature lowering step to thepressure vessel performing the heating up step.
 32. The batch wisemethod according to claim 31, wherein said hydrolyzing step is performedat a temperature of not lower than 140° C. and not higher than 180° C.to hydrolyze hemicellulose into saccharides.
 33. The batch wise methodaccording to claim 32, wherein: the slurry resulting from saiddischarging step is subjected to solid liquid separation; a slurrycomprising a solid content obtained after dissolution of hydrolyzedhemicellulose in water is prepared; the slurry obtained after the solidliquid separation is subjected to said discharging step again; and saidhydrolyzing step is performed at a temperature of not lower than 240° C.and not higher than 280° C. to hydrolyze cellulose into saccharides. 34.The batch wise method according to claim 31, wherein said hydrolyzingstep is performed at a temperature of not lower than 240° C. and nothigher than 280° C. to hydrolyze cellulose into saccharides.
 35. Thebatch wise method according to claim 31, wherein said charging stepincludes addition of ethanol in an amount of not less than 2 mol % andnot more than 10 mol % to the raw slurry.